Recently, an LCD or PDP is demanded from its application for a larger size as a display which is easy to view and more expressive, and from its manufacturing cost for higher yield from one substrate. To meet such demands, the substrate size is being made more and more larger for the panel. In particular, the PDP can be produced of a larger size than the LCD, a larger substrate is particularly demanded, which requires an efficient substrate transfer method in manufacturing a large substrate.
Now, an example of a conventional substrate transfer method is described with reference to the drawings.
FIG. 19 shows a substrate transfer method using a conventional substrate transfer cassette (hereinafter abbreviated to a "cassette") 10, a dolly 20, and a cassette holder 30 schematically shown in a side view. In the figure, the cassette 10 contains a plurality of substrates 1. Omitted in the figure is a tray for holding the substrates 1 with a pitch P. In addition, FIG. 19 shows a state where the dolly 20 loading the cassettes 10 has been automatically or manually moved from a position near a cassette holder (not shown) in the previous process to a position near the cassette holder 30 in the next process. Then, as shown in FIG. 20, the cassette 10 is moved over the holder 30 by extending arms 21a and 21b mounted on the dolly 20 in a direction of arrow A, and then placed on a predetermined position on the cassette holder 30 by lowering the arms 21a and 21b in a direction of arrow B. Reference numeral 31 denotes a recess for preventing interference between the arms 21a, 21b and the cassette holder 30. Furthermore, the arms 21a and 21b are retracted in a direction opposite to the arrow A and housed in the dolly 20 to attain the state of FIG. 21. Subsequently, the substrates 1 are aligned at the center of the cassette 10 in a direction orthogonal to a substrate entry/takeout direction (direction of arrow C) by a substrate aligning bar 32 mounted on the cassette holder 30. This is done to prevent the substrate 1 from striking against a side plate 11 of the cassette 10 shown in FIG. 22 when the substrate 1 is extracted from the cassette 10 in the direction of arrow A from the side opposite to the dolly 20 (HD side in FIG. 20) with respect to the cassette holder 30 as shown in FIG. 20 by a conventional robot (not shown), or to allow the robot to accurately place the substrate 1 extracted from the cassette 10 on a predetermined position on a substrate processing machine (not shown). The operation for aligning the substrates 1 is described with reference to FIG. 22 which shows a front view of FIG. 21. In FIG. 22, when the substrate aligning bar 32 is pushed in a direction of arrow D by an air cylinder (not shown) or the like, the substrate aligning bar 32 moves forward to a position 32a indicated by a chain line as shown in FIG. 23, and pushes both sides of the substrates 1 which have been unaligned until then as shown in FIG. 22, thereby positioning all the substrates 1 at the center of the cassette 10 in a direction (directions of arrows D and E in FIG. 23) orthogonal to the substrate entry/takeout direction (direction of arrow C in FIG. 21). Then, the substrate aligning bar 32 is driven in the direction of arrow E by an air cylinder or the like, and returned to its original position to complete the aligning operation.
However, with the arrangement described above, if length L of the substrate 1 in the cassette 10 shown in FIG. 19 becomes longer, the entire length S.sub.1 of the dolly 20 and the cassette holder 30 becomes very long. Since the cassette holder 30 is positioned near the substrate entry/takeout port of a substrate processing machine, if the number of substrate processing machines increases, the area occupied by the dolly 20 and the cassette holder 30 becomes too large, so that a large clean room is necessary. A large clean room increases not only its construction cost, but also the operation cost for maintaining cleanness, leading to high production cost.
In view of the above problem, the present invention is intended to provide a substrate transfer method and a substrate transfer cassette, which enable it to reduce the entire length of the dolly and the cassette holder.